Project Summary/Abstract Worldwide, approximately 466 million people suffer from disabling hearing loss. When conventional hearing aids provide no appreciable benefit, cochlear implants are a solution. Current cochlear implants, while beneficial in their use, are limited in their capabilities by hand-assembly of wire-bundled electrode arrays. Hand assembly is very costly, extremely labor-intensive, and inadequate in implementing new strategies in Otolaryngology for improving speech recognition and music appreciation. Advanced-manufacturing (microfabrication, laser-machining, etc.) has been deemed a superior replacement to the hand-assembly of electrode arrays, and many innovations have been made in this area. However, commercial suppliers have not adopted them. In large part, due to mismatches between the flat 2D bond pads of advanced-manufactured arrays and the 3D feedthrough pins of commercial stimulators. As such, they require additional adapters that not only reintroduce hand-assembly, but also add to the overall manufacturing costs and clinical failures. MEMStim LLC proposes a plug-and-play advanced-manufacturing solution that relies heavily on 3D printing. By printing conductive and nonconductive silicones, biocompatible pluggable arrays can be printed to any size, length, shape or thickness, from several microns to tens of millimeters. Most importantly, the integrated connectors plug readily onto stimulators by way of a novel micro-socket technology. The micro-sockets are compatible and slide right onto the feedthrough pins. The printer resolution can output pluggable connectors that are compatible with pin-to-pin pitches smaller than 100 m (edge-to-edge), allowing for enhanced miniaturization. In phase I work, high performing stimulating electrode sites and extension cables were demonstrated. Additionally, the feasibility of producing high performing plug-and-play connectors was demonstrated. The goal of this Phase II project is to monolithically integrate all three into the first-ever pluggable cochlear electrode array. The Aims of the Phase II grant are: (1) Produce an integrated 3D printed plug-and-play cochlear array that complies with the functional electrical requirements of cochlear implants; (2) Produce a 3D printed plug- and-play cochlear array that complies with the durability requirements of cochlear implants; and (3) Produce 3D printed plug-and-play cochlear array that complies with the biocompatibility and surgical safety requirements of cochlear implants. The end result will be the first-ever pluggable cochlear electrode array, which is functional and passes all the handling/use/safety tests that are necessary to seek approval from the FDA.